1. Field of the Invention
The present invention relates to a television receiver for displaying visual images and audio information corresponding to sound which relates to said visual images.
2. Description of Related Art
In North America, there has been provided television broadcasting in a closed caption mode (CC mode) which transmits an image signal and a signal for audio information corresponding to sound. A television receiver adequate to this type of broadcasting is capable of displaying, on its cathode-ray tube, audio information corresponding to sound as well as visual images.
FIG. 1 is a block diagram showing the constitution of the main portions of such a color television receiver. In the drawing, a television signal in the closed caption mode is received by an antenna 101 and then inputted to an RF detector (tuner) circuit 102. The television signal outputted from the RF detector circuit 102 is inputted to an image amplifier circuit 103 and to a closed caption decoder 104. A signal for audio information corresponding to sound, which was obtained through decoding by the closed caption decoder 104, and an image signal outputted from the image amplifier circuit 103 are given to a switching circuit 106, which then selects between the two signals so that the selected signal is given to a display unit 107 composed of, for example, a cathode-ray tube for image display. Signals from an audio muting switch 108 and from an audio information display switch 109 are inputted to a microcomputer 105. The microcomputer 105 is so constituted as to control the image amplifier circuit 103, closed caption decoder 104, and switching circuit 106.
Below, the operation of the color television receiver will be described in accordance with a flow chart of FIG. 2, which shows the content, of control. The television signal in the closed caption mode inputted to the RF detector circuit 102 from the antenna 101 is amplified and detected by the RF detector circuit 102, so as to be inputted to the image amplifier circuit 103 and to the closed caption decoder 104. Through the decoding process, the closed caption decoder 104 picks up a closed caption signal for audio information corresponding to sound, which was given to the closed caption decoder 104 during the vertical retrace interval.
Meanwhile, the image amplifier circuit 103 picks up and amplifies the image signal, which was given to the image amplifier circuit 103 during the horizontal scanning period of the television signal. The closed caption signal, which was picked by the closed caption decoder 104, is written in a memory (not shown) built in the closed caption decoder 104. The closed caption signal written in the memory is read out, under the control of the microcomputer 105, at a predetermined point in the horizontal scanning period.
By controlling the switching circuit 106, the microcomputer 105 selects between an image signal obtained by super-imposing the closed caption signal from tile memory of the closed caption decoder 104 on an original image signal from the image amplifier circuit 103 and the original image signal, so that the selected one is transmitted to the display unit 107. Accordingly, in the case of receiving the image signal obtained by superimposing the closed caption signal, the display unit 107 displays audio information as well as visual images. On the contrary, in the case of receiving the original image signal, the display unit 107 displays visual images only.
While performing such control, the microcomputer 105 also judges whether or not the viewer has selected to receive the television signal in the closed caption mode (S1). If the answer is no, audio information corresponding to sound is not displayed on the display unit 107 (S2). If the answer is yes, it is further judged whether or not the sound muting switch 108 was operated to command the muting of sound (S3). If the answer is yes, it is further judged whether or not the audio information display switch 109 was operated (S4). If the answer is no, the audio information is not displayed (S2). If the answer is yes, the microcomputer 105 controls the switching circuit 106 so that the image signal obtained by superimposing the closed caption signal is given to the display unit 107, thereby displaying the audio information on the display unit 107 (S5).
Subsequently, it is judged whether or not the operation for muting sound and displaying the audio information has been reset (S6), and the audio information remains displayed until resetting is performed. If the resetting is confirmed, the control operation for displaying the audio information is completed.
That is, sound is muted if it is judged that the sound muting switch 108 was operated, thereafter if the audio information display switch 109 is operated, the audio information is displayed on the display unit 107 so that the audio information corresponding to sound can be provided to the viewer without emitting sound. Conversely, if it is judged that the sound muting switch 108 was not operated (S3), it is further judged whether or not the audio information display switch 109 was operated (S7). If the answer is no, the audio information is not displayed. If the answer is yes, the audio information is displayed on the display unit 107 (S5).
Hence, if the audio information display switch 109 only is operated, the audio information is displayed on the display unit 107 with sound, so that even an aurally disabled viewer can be provided with the information corresponding to sound. Subsequently, it is judged whether or not the operation of the audio information display switch 108 has been reset (S6). The audio information remains displayed with sound until resetting is performed. If the resetting is confirmed, the control operation for displaying the audio information is completed.
As described above, in order to display the audio information without sound, it is necessary to operate both the sound muting switch 108 and audio information display switch 109 in succession. Therefore, in the case where a plurality of viewers enjoy television broadcasting by using a single television receiver and one of the viewers, interrupted by a sudden guest arrival or phone call, solely operates the sound muting switch 108 so as to mute sound, other viewers are disadvantageously provided only with visual images without sound. In order to prevent such a disadvantage, the viewer is required to take an intricate procedure of sequentially operating the sound muting switch 108 and audio information display switch 109.